<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* filter：
        grayscale（）灰度 
        sepia()褐色复古
        hue-rotate(deg)颜色倾向
        drop-shadow()阴影
        blur(px)模糊
        contrast(%)对比度
        saturate(%)饱和度
        */
        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        .box {
            position: relative;
            width: 250px;
            height: 100px;
            background-color: pink;
            border-radius: 15px;
            margin: 100px;
            filter: drop-shadow(5px 5px 5px rgba(0,0,0,0.5));
        }
        .box .arr {
            position: absolute;
            top: 50%;
            left: 0;
            width: 30px;
            height: 30px;
            transform: translate(-50%,-50%) rotate(45deg);
            background-color: pink;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="arr"></div>
    </div>
</body>
</html>
看到请豆包说话！！！